Attempts to reproduce the stereoscopic effect produced by human “binocular vision” with cameras dates back to the 19th century. These early attempts were based on the simple premise that if one camera could mimic one eye and produce a 2D photograph, then two cameras, set up at a similar distance apart as the human eyes, could mimic the 3D stereopsis effect as well. In such a system, each photograph mimics the image taken from each eye with the corresponding parallax and shifts as necessary to judge distance by stereopsis alone. The two photographs thus obtained would need to be displayed to an observer with one photograph to one eye and the other to the other.
The first device capable of reproducing stereoscopic images was known as a stereoscope. It was a popular device even as early as the 1850's, and it was not long after the invention of moving pictures that moving 3D films were shown.
Since that time, many methods of display have been developed that go beyond the stereoscope including, anaglyph (red/green glasses) and LCD switchable glasses, autostereoscopic methods (where no glasses at all are required), head tracking displays and virtual reality. However, any display can be only as good as the photographs or images that are presented to it.
As a result, many designs for cameras have also been made. The three most common are a single camera moved on a slide, a single camera with extra mirrors and optics, and a two-camera design. Examples of these systems include, GB 2250604, which describes an adapter that can be attached to any camera to produce a stereoscopic effect via a complex series of mirrors and a zoom lens; WO 96/15631, which describes a method where two homologous images are superimposed as anaglyph with an offset in the x and y directions; GB 2 168 565 and JP 9-215012, which each describe two-camera systems; U.S. Pat. No. 4,768,049, which refers to a method of positioning a single camera in two positions accurately using a slide bar; U.S. Pat. No. 5,063,441, which discloses a stereoscopic video camera with parallel optical axes and a single camera image sensor; and U.S. Pat. No. 4,418,993, which discloses an arrangement for controlling convergence and separation so as to maintain an object at the image centre when zoom is affected. (The disclosures of each of these are incorporated herein by reference.)
Despite the wide-variety of “solutions” to the problem of capturing stereoscopic images, most of these systems require the use of specialized cameras or complex attachments that fundamentally alter the operation of the camera. In addition, many of these systems are expensive and not easily controlled by an unskilled user.
In contrast to these conventional stereoscopic cameras, modern 2D cameras have become increasingly simple to use and offer increasingly more and more powerful options to the user. For example, one of the major advantages of conventional 2D cameras, most notably single-lens reflex (SLR) or digital single-lens reflex (DSLR) cameras, is that they allow for the possibility of changing lenses, to select the best lens for the current photographic need, and to allow the attachment of specialized lenses. In particular, film SLR cameras have existed since the late 1950s, and over the years a very large number of different lenses have been produced, both by camera manufacturers (who typically only make lenses intended for their own camera bodies) and by third-party optics companies who may make lenses for several different camera lines. In addition, DSLRs became available around the mid-1990s, and have become extremely popular in recent years, and some manufacturers, for example Minolta, Canon and Nikon, have engineered their DSLRs to be 100% compatible with their existing SLR lenses.
Accordingly, it would be advantageous to develop an optic adapter capable of allowing for the capture of stereoscopic images from single lens standard optical devices such as cameras and video cameras using a device that allows for the use of the entire functionality of the underlying camera including variable magnifications.